A problem of high voltage power cable systems in ground (for instance operating with a voltage of at least 10 kV, usually above 110 kV or 220 kV up to 500 kV or higher) is the effect of partial discharge which can destroy the electric cable over time.
Conventionally, partial discharge is measured electrically, with different sensor, like current transducers, high frequency probes and ultrasonic acoustic point microphones.
U.S. Pat. No. 5,386,193 discloses a partial discharge detecting device for a resin-molded transformer having no-load switching tap terminals on a high voltage winding thereof. An amplifier amplifies the output detection signal of a partial discharge detecting sensor connected between the tap terminals, and an electro-optic converter converts the output signal of the amplifier into an optical signal. The optical signal is applied through an optical fiber to an opto-electric converter where it is converted into an electrical signal. The electrical signal is applied to an indicator. The partial discharge detecting sensor, the amplifier circuit, and the electro-optic converter are held at a potential corresponding to a potential of the tap terminals.
US 2005/0134837 A1 discloses a cable for detecting partial discharges or arcing in wiring or cables via fiber optics. The cable for detecting partial discharges includes a conductor for carrying electrical signals, at least one fluorescent optical fiber for detecting light generated by a partial discharge, and a first transparent layer surrounding the conductor for supporting the at least one fluorescent optical fiber generally parallel to the conductor. By employing a fluorescent optical fiber, incident light generated by a partial discharge along a length of the optical fiber will be transmitted via the optical fiber to an optical receiver for determining a partial discharge has occurred.
US 2009/0102489 A1 discloses a distributed sensing system for detecting partial electric discharge along the length of an extended object or objects. An optical fiber having a cladding integrated with luminescent material and a silica core of less than 500 micrometers in diameter with a first reflective end deployed in proximity to test objects. A photodetector is positioned at the second end of the optical sensing fiber and receives and measures both a direct emission light from an electric partial discharge event and the reflected emission light from the reflection end of the optical sensing fiber. The measured signals and their arrival times are used to determine the location and magnitude of a partial electrical discharge.